The Ian Healy youtube video is handy, I remember using that a few moons ago.
Basics though, staying low being a key and being comfortable (often underestimated as far as I'm concerned, when I'm in a good position I keep well).
Most important of all though is footwork. As I say to the youngsters I coach, if i was to throw a ball three foot to your left and you dive to get it you'll catch it 5/10, whereas if your footwork was proactive and you made most of the distance before having to resort to diving you'll catch 9 or 10/10.
Obviously this is aimed at lower level youngsters but the advice is true to anyone.